1. Field of the Invention
The present invention relates in general to reservoir optimization and more specifically to petroleum wells having downhole independently addressable wireless measurement and control devices that communicate with surface power and telemetry devices such that production from individual zones within individual wells may be coordinated to optimize overall reservoir production.
2. Description of Related Art
Oil and gas reservoirs are extensive three-dimensional subsurface geological structures whose fluid contents are produced through arrays of wells which withdraw fluids from the reservoir only at points where the wells pass through the producing zones. As fluids are withdrawn at the wells, pressure differentials develop within the reservoir which in turn create displacement of fluids from more distant reservoir regions towards the producing wells. To assist in sweeping desired fluids towards the producing wells, it is common practice in some fields to pump water or other fluids into wells which are designated injection wells.
To assist in comprehending the changing condition of the reservoir and thus manage production from individual wells to optimize recovery from the field overall, it is common practice to develop a reservoir model which reflects the relevant characteristics of the formation's fixed matrix such as porosity and permeability, and the composition, pressure, and temperature of the fluids contained within that matrix. The parameters of both the matrix and the fluids are expected to change as fluids are withdrawn from the producing wells and injection fluids are introduced at the injection wells. Since the geological formations of the reservoir are generally heterogeneous, the starting values of the matrix and fluid parameters are spatial variables, and as production evolves the changes in these parameters are also spatially variable in addition to being time dependent.
The data used to generate a reservoir model come from many sources. Three-dimensional seismic surveys provide stratigraphy and faulting, and wireline logging, existing well production histories provide, and to a lesser extent seismic surveys, provide data on formation fluids.
The starting values of the reservoir model parameters adjacent to each well can be measured relatively easily using wireline logging tools before each well is cased, but once production has commenced the presence of the well casing prevents many of the measurements which can be made in an open hole. Even measurements which could be made through the casing are usually not performed in existing practice since doing so would require either removing the production hardware and tubing from the well and running cased hole wireline logs, or the use of permanent downhole sensors connected to surface equipment by cables which extend the full depth of the well. These cables are expensive, are not entirely reliable, often introduce operational problems, and their installation at the time of completion complicates that process. The same issue of requiring cables to operate downhole control equipment such as valves also discourages the use of such devices. When downhole control devices are absolutely required, the provision of permanently installed cables can be avoided by using slickline tools, but cost prevents these from altering the settings of downhole devices at frequent intervals.
All references cited herein are incorporated by reference to the maximum extent allowable by law. To the extent a reference may not be fully incorporated herein, it is incorporated by reference for background purposes and indicative of the knowledge of one of ordinary skill in the art.